Combating rabies and
other tick diseases

There are many species of tick - this is just one of them.

Recognising this, the world's largest medical charity - the United Kingdom-based Wellcome Trust - supports international veterinary as well as medical research. Much international veterinary research is also sponsored by the government-financed Biotechnology and Biological Sciences Research Council.

Among research being sponsored by the Wellcome Trust is an investigation of how best to administer vaccination against rabies in Ethiopia, where the disease is a considerable public health problem, with more research to discover what wild species act as reservoirs of disease.

Another Wellcome-sponsored research project, in Tunisia, aims to discover more about the common tick-borne disease caused by the parasite, Theileria, which is common in much of the tropical world. One long-term aim is to develop improved methods of vaccination against the parasite.

The Wellcome Trust recently launched an awareness-raising initiative to make potential applicants around the world aware of the scope of research opportunities sponsored by the trust and which may be open to them. There are opportunities for scientists based outside the UK with research interests in animal health to receive further training, as well as sponsorship for their research. And there are schemes that specifically encourage studies in developing countries.

Some examples of veterinary research funded by the trust and already in progress should give an idea of the variety of support available and the broad geographical spread of trust-funded veterinary research. More than 90 per cent of human cases of rabies in Ethiopia are caused by transmission from dogs. Rabies also causes significant economic losses when livestock are infected.

Recent epidemics in the endangered Ethiopian wolf and in African wild dogs have raised concern about the impact of rabies on the conservation of rare species.

Karen Laurenson of the Royal School of Veterinary Studies in the University of Edinburgh, Scotland, has been awarded a Wellcome research fellowship in tropical medicine to study the ways in which the rabies virus is transmitted from domestic and wild dogs and possibly other animals to humans, in the Bale Mountains National Park, Ethiopia.

This area encompasses several towns and is home to numerous wild carnivores, including the Ethiopian wolf, a critically endangered species. This makes it a good area to try to discover what other species besides domestic dogs, jackals, civets, mongooses, wolves, foxes, hyenas and possibly others may be acting as reservoirs of infection.

If this research shows that wild species rather than domestic dogs are the main reservoirs, then vaccinating even a large proportion of domestic dogs will not eliminate the risk of infection.

It will always re-enter the domestic population from the wild. Clearly, the reservoir or reservoirs have to be identified before the best and most economical control measures can be decided. Dr Laurenson's work is sure to have relevance to and potential value for other areas besides Ethiopia. Theileria is the name of a family of single-celled parasites which cause some of the most important diseases of domestic livestock worldwide.

Theileria are carried by bloodsucking ticks which enter an animal's bloodstream when the tick feeds, and invade blood cells causing weight loss, anaemia and, frequently, death.

In Tunisia a less-virulent strain of Theileria annulata, one of the parasites responsible for disease - which has been obtained by long-term culture of an infected cell line - is already being used in a protective vaccine. Dr Chris Oura has been awarded a Wellcome advanced training fellowship in tropical medicine at the University of Glasgow to discover why this cell line is so much less pathogenic than the normal parasite, yet is still able to stimulate immunity powerfully so it can be used in a vaccine. Normally the Thelleria parasite, as so many other parasites, assumes different forms with different properties at different stages of its life cycle.

Dr Oura is researching to see if it is an inability to differentiate into two critical stages of its life cycle, due to genetic changes, which renders the cultured form of Theileria used in vaccine much less pathogenic, while still able to stimulate immunity. The better understanding of the mechanisms of immunity this provides will, it is hoped, help in the development of better vaccines.

Another UK agency that funds much veterinary research of benefit to and with links to countries beyond the UK is the govemment-funded Biotechnology and Biological Sciences Research Council (BBSRC). A team of BBSRC-sponsored scientists at the Institute for Animal Health at the Compton Laboratory, southern England, has recently developed a vaccine able to protect chickens against the common intestinal parasitic disease of coccidiosis. This will do away with the need to treat poultry with a cocktail of powerful drugs, thus benefiting both chicken farmer and consumer.